Abstract: The species abundance pattern of plant community was analyzed under different stocking rates in Inner Mongolia Stipa breviflora desert steppe by using filed investigation and geometric model, segmentation model and niche overlap model, in order to know species interrelation and community pattern, and to reveal the effect of overgrazing on desert steppe community. The results showed that the geometric model well fitted the species abundance pattern of plant community under different stocking rates in S. breviflora desert steppe. With the increasing stocking rate, the species abundance pattern didn’t change, but the plant frequency decreased. The species numbers were lower in moderate and heavy grazing treatments than in the control and light grazing treatments. The dominant species S. breviflora played a key role in plant community pattern in desert steppe. Heavy grazing decreased the overall community frequency but increased the dominant species frequency.

Key words: nitrogen use efficiency, grain yield, reduced nitrogen rate, wheat, postponed basal fertilizer